Second Law of Thermodynamics:States that the total entropy of an isolated system can never decrease over time and is constant if all processes are reversible.
$Q_{rev}$: $Q_{rev}$ denotes reversible heat transfer, which occurs without increasing the total entropy of the system plus surroundings.
$\Delta S$: $\Delta S$ represents the change in entropy, often used to quantify how much disorder or randomness has increased or decreased within a system.